Hi Raj,
"Warm" is a euphemism for plump, "fat" or muddled bass output, which the B&Ws (and lots of other speakers) exhibit and which I liked as a kid but grew weary of very quickly when I discovered neutral, transparent speakers with linear bass that isn't "goosed".
So yes, the M22s aren't as "warm" as the B&W 603s; they are just more linear and natural.
If you used the M60s, even with a subwoofer, you'd get more authoritative bass than the M22s. Crossovers are gradual, so even if you set the M60s to "Small" (just like my M80s, which are set to "Small") and use a sub, you'll still get fuller (but not "fat") bass extension. The mids and highs of the M60s will be similar but not quite identical to the M22s. The latter have a teensy-weensy bit more articulation in the upper mids than the M60s, but it's only audible on instantaneous A/B comparisons.
Regards,
